1. Field of the Invention
This invention relates to a cooling method and a system therefor, more particularly to a method of suitably operating a cooling system including freezers, coolers and refrigerators, each provided with an air-cooled condenser and a water-cooled condenser and also to a system for suitably embodying the method,
2. Description of the Related Art
(First Background of the Invention)
In a refrigerant circuit of a freezer so far known, for example as shown in FIG. 6, a refrigerant is designed to repeat the following circulation cycle: a vaporized refrigerant compressed in a compressor 1 is fed to an air-cooled or water-cooled condenser 2 and condensed thereby; the refrigerant thus liquefied is fed to an expansion valve 3 to undergo volume expansion and then evaporated in an evaporator 4 so as to allow the evaporator 4 to perform a freezing operation or ice making operation; and then the vaporized refrigerant is fed back to the compressor 1. In the case the condenser 2 is of an air-cooled system, if the capacity of the compressor 1 is increased so as to improve freezing performance of the freezer, the capacity of the condenser 2 must be increased concomitantly. Accordingly, the outer dimensions of the freezer are inevitably increased greatly. Since the quantity of heat to be exhausted from the condenser 2 is also increased, the temperature of the kitchen or machinery room is elevated to worsen the working environment, in turn, to lower the cooling capability of the condenser itself, affecting the performance of the freezer. It can also be pointed out that the power consumption increases due to the increase of the load of cooling in the kitchen. Meanwhile, in the case the condenser 2 is of a water-cooled system, there is a problem that the freezing cost increases due to the increased amount of cooling water employed.
In the refrigerant circuit of the freezer shown in FIG. 7, a vaporized refrigerant compressed in a compressor 1 is allowed to pass a water-cooled condenser 5 and an air-cooled condenser 6 successively and condensed thereby, and the downstream circulation system is of the same constitution as the one shown in FIG. 6. In this case, opening and closing of a self water feeding valve 7 for supplying a cooling water to the water-cooled condenser 5 is controlled depending on the temperature or pressure of the liquefied refrigerant flowing out of the air-cooled condenser 6. For example, if the temperature or pressure of the liquefied refrigerant drops below a preset value, the self water feeding valve 7 closes to interrupt feeding of the cooling water to the water-cooled condenser 5. Thus, the cooling water dwelling in the water-cooled condenser 5 is heated to a high temperature by the hot vaporized refrigerant fed from the compressor 1, If the thus heated cooling water is discharged from the water-cooled condenser 5, the drain pipe may be bent by the heat of the hot cooling water, or the adhesive for piping may melt to cause leakage in the drain pipe, bringing about troubles such as damage of the carpet laid on the floor on which the freezer is installed. Meanwhile, it can also be pointed out that the water vapor thus formed is condensed into dew drops around the outlet, which gather and drop in the form of droplets, disadvantageously. These unfavorable phenomena described above are liable to be caused upon temperature rise of the cooling water in the water-cooled condenser 5 to 60.degree. C. or higher, even if the self water feeding valve 7 repeats opening and closing around the preset temperature or pressure level.
Next, in the refrigerant circuit of a freezer shown in FIG. 8, a vaporized refrigerant compressed in a compressor 1 is designed to be condensed by first passing it through an air-cooled condenser 6 and then through a water-cooled condenser 5, and the downstream circulation system is of the same constitution as in FIG. 6. The water-cooled condenser 5 is provided with a similar self water feeding valve 7 to the one shown in FIG. 7. In the thus constituted refrigerant circuit, however, the hot vaporized refrigerant discharged from the compressor 1 is all passed through the air-cooled condenser 6 to allow heat dissipation to occur therein as much as possible, irrespective of the level of the ambient temperature. Accordingly, the same inconveniences as in the case of the air-cooled system condenser 2 shown in FIG. 6 can be pointed out. Moreover, since a large amount of cooling water must be supplied to the water-cooled condenser 5, the running cost elevates, disadvantageously.
If the temperature or pressure of the liquefied refrigerant passing through the water-cooled condenser 5 drops below the preset level and the self water feeding valve 7 is closed, the refrigerant is already liquefied at the outlet of the air-cooled condenser 6, resulting in the increase of the downstream piping volume due to the presence of the water-cooled condenser 5. In this case, the amount of the refrigerant to be sealed in the circuit must be increased compared with the case where the vaporized refrigerant is first passed through the water-cooled condenser 5 like in the refrigerant circuit shown in FIG. 7, leading readily to homing etc. when the circulation of the stagnated refrigerant is started and to a liability to damage of the compressor 1, impairing reliability of the freezer, disadvantageously.
The same inconveniences as described above cannot be obviated, if the evaporator 4 is allowed to carry out a defrosting or ice removing operation even in an ice making machine in which a hot gas piping system which passes by the condenser 2 (5,6) and the expansion valve 3 and connects the outlet side of the compressor 1 directly to the inlet side of the evaporator 4 may be provided on each of the refrigerant circuits described above, and the hot gas valve provided on the piping system is let open to introduce the hot vaporized refrigerant fed from the compressor 1 to the evaporator 4.
(Second Background of the Invention)
The cooling system according to the prior art described in Japanese Unexamined Utility Model Publication (Kokai) No. 85-188623 is provided with a dual condenser, and one condenser unit is provided with a refrigerant by-pass, with an electromagnetic valves being disposed on the refrigerant by-pass and to the upstream side of said one condenser unit. In the constitution disclosed therein, these electromagnetic valves are opened and closed alternately, and the dual condenser or only the other condenser unit is operated based on the opening and closing operations of these electromagnetic valves. However, in this constitution, extra equipment including the refrigerant by-pass, switching electromagnetic valves, etc. are required, leading to the cost elevation.
Meanwhile, in the constitution of the prior art cooling system provided with an air-cooled condenser 6 and a water-cooled condenser 5 as described referring to FIGS. 7 and 8, the air-cooled condenser 6 is constantly operated, and the water-cooled condenser 5 is also additionally operated in such cases where the cooling performance is insufficient and the like. Accordingly, if the refrigerator and the like is installed in a small kitchen, the room temperature of the kitchen is elevated due to the heat exhausted from the air-cooled condenser 6 when the ambient temperature is high like in the summer to worsen the working environment in the kitchen. Thus, the cooling load in the kitchen must be increased.
In the above-described prior art cooling system provided with an air-cooled condenser 6 and a water-cooled condenser 5, if the fan motor for the air-cooled condenser 6 breaks down for some reasons or other, the insufficient cooling to be brought about thereby is automatically compensated by the water-cooled condenser 5. Accordingly, if the operation of the refrigerator is continued without the breakdown of the fan motor being noticed, the amount of the cooling water to be consumed in the water-cooled condenser 5 increases extremely, and it is not until the increase of the water consumption is noticed that the breakdown of the fan motor is recognized. Further, if the fan motor for the air-cooled condenser 6 is looked, the electric current continues to flow into the motor to cause overheating thereof, leading to the liability of burning of the motor.